Heating apparatuses are known for heating buildings as a substitution for the usual thermo-hydraulic heating systems that utilize wall mounted diffuser elements.
These heating apparatuses comprise very thin diffuser panels, which are normally powered by electricity and are installed under the surface of a wall or a floor; therefore, these apparatuses radiate heat in the rooms by heating them by means of heat conduction.
According to the patent PCT/IT02/00735 a band system is known for heating that comprises a band body which is substantially thin, formed by a pre-established number of layers of different materials coupled together and, more precisely, by a thin sheet of conductive metal material which is folded over on itself to form two parallel approachable laps that have a mutual end, where the fold is made, which is connected without interruption, and two opposite free ends.
In addition, between these two laps is placed a thin sheet of polyester that acts as electrical insulation and lastly two layers of bituminous material are applied externally, by dipping, that completely coat the two outer faces of the two laps.
At the free ends of the latter, two respective terminals are to be mounted that are for connecting, by means of electrical cables, to a low voltage electrical power supply device that can be placed in a special seat obtained in the walls of the rooms which are defined in the buildings and which has a switch for turning heating on or off and possibly also a regulator to allow the users to regulate the intensity of the electricity travelling through the two laps and, consequently, their heating temperature.
The band is flexible and positioned, e.g. under the concrete pavement that supports the coating material of a floor.
The band is put in place before the concrete pavement is laid, laying it normally according to the sides of the surface to cover and substantially over the whole surface available.
To make a substantially complete covering of the surface, since, although it is flexible, the band is unable to follow curves on a flat surface, the band is folded over on itself at the boundary areas, i.e. the perimeter walls, at 45° angles so that, with one or two folds made in succession, a path is created either in a coil, that comprises segments going away and other parallel segments returning, or segments in succession arranged in a spiral.
The widths and lengths of the sheets that form the layers are all the same, so a band is created that is substantially uniform at all points.
This state of the art has a drawback which is the need to obtain, after the band has been made, areas of free ends of the conductive metal material sheets that have no bituminous coating, so the terminals can be mounted on such uncoated areas and the conductive contacts can be made between the terminals and the sheets.
To eliminate the portions of bituminous sheets that cover these respective areas, a very low temperature gas is sprayed on them so that the bituminous material, getting really cold, becomes brittle and easily breakable and can be removed according to a precise design, uncovering the areas required.
This gas is very expensive and the whole procedure to remove the bituminous material which is firmly stuck on the areas of the faces of the sheets of conductive material takes a long time and is very difficult.
Another drawback is that if, when laying, the band is drilled accidentally or even intentionally to make some elements of the construction protruding in relief pass through a hole obtained in the band, the two laps of conductive metal material can be connected in short circuit with each other if the material of the construction element is also metal, acting as an electric bridge between the laps.
This short circuit leads to an increase in temperature of the sheets of conductive metal material concentrated in areas where the construction element goes through, in this specific case around the edges of the hole.
This increase in temperatures leads to the progressive burning of both sheets of conductive metal material which are very thin.
Burning extends progressively to a certain extent of the surface surrounding the hole and, due to the heat produced, tends to melt the sheet of polyester that acts as insulator.
This can determine the creation of areas without insulation among the sheets of conductive metal material and the consequent widening of the areas of direct contact between the two sheets of conductive metal material.
Such widening can extend up to the whole width of the band with the risk that, in those areas where the width of the band is reduced, the flow of electricity interrupts and, therefore, the working of the whole heating apparatus or part of it is also interrupted.
When this damage is done, to restore working of the heating apparatus, it is necessary to remove the surface that covers it, e.g. a floor, with serious damage and discomfort for the users who find themselves without heating and having to prepare the masonry for band repairs.
In addition, concentrated heating caused by a short circuit softens all the external bituminous covering layers, when nets are used—normally the case in masonry structures that cover the heating apparatus—and this softening happens, it causes these nets to be incorporated into the bituminous layers until they come into contact with the sheets of conductive metal material and, creating other short circuiting points which, if very close to one other can, in this case, interrupt the conduction of electricity and the production of heat.
Another drawback of the known technique is that due to the meltability of the bituminous covering layers, these known devices cannot be used to heat surfaces over which vehicles travel, such as roads and car parks, or airport runways, to keep them free from ice and snow.
The reason for this is that roads and runways are covered with layers of bituminous surfaces at the fluid or plastic state at very high temperatures, about 200° C., and these temperatures would melt the bituminous covering layers of the heating apparatuses, damaging them irreparably.
Another drawback of the known technique is that the band weighs a lot and this creates difficulties in handling, transporting and laying it.